1. Field of the Invention
The present invention relates to an information reproducing apparatus for playing back a recording medium, such as a CD (Compact Disk), and, more particularly, to a CD player capable of playing back a partially recorded CD-R (CD Recordable) which is of a DRAW (direct read after write) type.
2. Description of Background Information
CDs are well known as a recording medium on which audio data or the like is recorded. The CD has a lead-in area where index information of recorded data is recorded, a program area where actual musical data is recorded, and a lead-out area indicating the end of the program area, formed on the CD in order from the inner periphery of the disk, as shown in FIG. 1. A signal to be recorded is a digitally modulated by EFM (Eight to Fourteen Modulation). The signal includes a main code (main information) such as musical data, and a subcode such as a time code (time information). Index information called TOC (Table Of Contents) is recorded in the lead-in area. The signal the total number of pieces of recorded information (e.g., the total number of music pieces), the total program time (e.g., the total playing time), etc. are recorded as the subcode also in that area. Musical information or the like is recorded as the main code in the program area. A track number (TNO) indicating the number of each piece of recorded information (e.g., the music number), the program time (P-TIME) from the beginning of the track, such as the playing time of the music piece, the total program time (A-TIME) measured from the first track number (=1), such as the total playing time, etc. are recorded in the Q channel of the subcode in the program area PA. A lead-out code indicating the lead-out area is recorded in the lead-out area.
While a CD having the above-described recording format is a read-only recording medium, a writable CD-R having the same format as the CDs has been developed recently. This CD-R recording format standard is standardized into a so-called "Orange Book", which Conforms to the CD format standard (called a "red book"). The CD-R disks are classified into the following three types as shown in FIG. 2A to FIG. 2C depending on the recording status. More specifically, the first type is a blank or unrecorded disk where no information has been recorded, as shown in FIG. 2A. The second type is a partially recorded disk (hereinafter referred to as "PRD" ) where information is partially written, as shown in FIG. 2B. The last one is a finalized disk for which recording is complete and which has been formatted in substantially the same format as CDs. As illustrated in those diagrams, the lead-in area, program area and lead-out area are also formatted on each CD-R in the same manner as that of CDs.
A pregroove is formed on the recording track of a CD-R, and it is wobbled by a frequency that is acquired through FM modulation of a carrier with data indicating the absolute time information (ATIP: Absolute Time In Pregroove). In a CD-R recording and playback apparatus, the tracking control and spindle control are performed according to the pregroove so that information is recorded on and read from a blank disk as well as a PRD. A PMA (Program Memory Area) as a temporary TOC area to store the recording history of recorded information is provided on the PRD on the inner periphery side of an area I that is reserved for the lead-in area LIA as indicated in FIG. 2B. In this PMA, the following three types of information are recorded. The first information includes the start and end addresses of information recorded in the program area, which are recorded in the same format as TOC information that is recorded in the lead-in area. The second type is disk identification information (optional) which may be 6-digit numeral information to identify a disk as needed. The third type is skip information and skip release information, which are associated with a command to skip the recorded information track by track that indicates a movement, or part of each track indicating a movement (time can be designated in the latter case) at the time of playing back the disk. The reason for recording such information as temporary TOC in the PMA is that since information is writable in the remaining program area on the PRD, TOC information cannot be recorded in the lead-in area LIA until the finalization of recording is instructed.
Prior to Finalization, no information is written in the lead-in area I and the lead-out area 0 of a PRD. Therefore, those areas remain in a mirror-finished state. When a command for finalization is given, the CD-R recording apparatus records predetermined information and TOC information recorded in the PMA as a subcode in the lead-in area I, and records a predetermined lead OUT code indicating the lead-out area LOA in the area 0 for the lead-out area LOA in order to provide the same format as that of CDs at last. This allows the conventional CD player to play back the finalized CD-R.
Further, as shown in FIG. 3, when a reverse (REV) command is input during playback of the CD-R to return the pickup to the head address of the program area of the CD-R to start reproduction (step 105), it is checked if the pickup is positioned on the lead-in area (step 106). The decision of step 106 is made by detecting the lead-in area as the inner peripheral edge of the disk. When the pickup position is detected to be on the lead-in area, the reverse command is canceled and playback is carried out (step 110). When the pickup position is detected to be off the lead-in area in step 106, a reverse operation is performed to cause the pickup to sequentially jump back to the head address of the program area (step 109). Those steps 106 and 109 are repeated until the pickup position is detected to be on the lead-in area.
The conventional CD player cannot reproduce reproducible information from a PRD though that information is stored in the program area PA because of the following reasons. Although a PRD has TOC information recorded in the PMA provided on the inner periphery side of the lead-in area, the conventional CD player is equipped with no mechanism to access that PMA. In addition, the area I for the lead-in area LIA and the area 0 for the lead-out area LOA remain mirror-finished and the conventional CD player is not designed to perform the proper control on information reading from such areas so that loss of control of the servo system may occur when reading information from those areas. Even if the setup is properly done for a PRD, the conventional CD player cannot properly control information reading from the PRD. A reverse command to return the pickup to a predetermined address on the PRD for playback moves the pickup over to the mirror-finished lead-in area, and causes loss of control of the servo system.
To solve this problem the CD player may be equipped as a CD-R recording and playback apparatus with the mechanism to access the PMA and some means to read the pregroove and perform the tracking and spindle controls. Providing a special device only for the PRD is not cost effective.